Recording / playback apparatus, playback apparatus, computer-readable recording medium, program and method

ABSTRACT

A recording/playback apparatus for a DVD on which a VOB and a management file of the VOB are recorded. When detecting a failure in the management file, the recording/playback apparatus changes the state of the DVD to: (a) a first state in which reading/writing of the DVD is available; (b) a second state in which reading/writing of the DVD is available but the VOB cannot be played back; or (c) a read only state, in accordance with the detected failure. When the state of the DVD changes to the second state, the recording/playback apparatus writes a new VOB onto the DVD. When the state of the DVD changes to the read only state, the recording/playback apparatus plays back the VOB recorded on the DVD.

BACKGROUND OF THE INVENTION

[0001] (1) Field of the Invention

[0002] The present invention relates to a recording/playback apparatusfor recording and playing back data to/from a rewritable optical discsuch as DVD-RAM, DVD-R, and DVD-RW.

[0003] (2) Description of the Related Art

[0004] Recording/playback apparatuses for rewritable optical discs canperform variable playback operations such as special playback and randomaccess operations and can also perform variable editing operations suchas virtual and real editing operations, by accessing discs conforming tothe DVD-VIDEO RECORDING standard. Such recording/playback apparatuseshave enormous values as commercial products. In such recording/playbackapparatuses, the program for performing recording, playback, and editingpresumes that the video data and management information recorded on theDVD has a data structure that conforms to the DVD-VIDEO RECORDINGstandard. The program fails to operate normally when trying to play backor edit data without a data structure that conforms to the DVD-VIDEORECORDING standard.

[0005] When a DVD recording video data is inserted, a recording/playbackapparatus performs an initial check to see whether the video data andmanagement information recorded on the DVD conforms to the DVD-VIDEORECORDING standard and whether the DVD has a portion that does notconform to the DVD-VIDEO RECORDING standard. The serious failures foundthrough this inspection include: (1) destruction of the managementinformation used for accessing the video data; (2) destruction of themanagement information related to playing back of the video data; (3)incorrect addresses of the video data or the management information; and(4) incorrect time codes of the video data. It is well known that suchfailures are caused by the dust or flaws on the disc surface. Thegeneral versatility of the DVD that the DVD can be accessed by evencommercial personal computers is one of the main selling points of theDVD. Accordingly, a failure occurs when a personal computer writes datathat violates the standard. There is another serious failure which iscalled a version confliction where the video data or the managementinformation recorded on the disc conforms to a DVD-VIDEO RECORDINGstandard that is higher than the versions that the recording/playbackapparatus can deal with. This failure can also interfere the normaloperation of the recording/playback apparatus.

[0006] When a serious failure such as the destruction of the managementinformation is found in the initial check of the inserted disc,conventional recording/playback apparatuses regard the DVD as an invaliddisc. The recording/playback apparatus does not read nor write datafrom/to the “invalid disc”, without recognizing it as a medium. Whenthis happens, the inserted DVD is treated in the same way as a recordingmedium that cannot be accessed by the recording/playback apparatusphysically. Accordingly, to use the DVD, the user must initialize theDVD. With such initial check and recognition of discs with failures asinvalid discs, it is possible to prevent the program loaded onto therecording/playback apparatus from hanging up. This increases thereliability of the recording/playback apparatus.

[0007] However, when light failures are treated in the same way as theserious failures, users would be required to initialize DVDs frequently.

[0008] On the contrary, when light failures are overlooked, users wouldworry that the playback/recording/editing program may start to operateabnormally at any moment.

SUMMARY OF THE INVENTION

[0009] The object of the present invention, therefore, is to provide arecording/playback apparatus that can appropriately operate inaccordance with a failure that may be detected in the video data or themanagement information recorded on an optical disc.

[0010] The above object is fulfilled by a recording/playback apparatusfor an optical disc on which a video object and management informationof the video object are recorded, the recording/playback apparatuscomprising: a detecting unit operable to detect a failure in themanagement information recorded on the optical disc inserted in therecording/playback apparatus; a state transition control unit operableto change a state of the inserted optical disc to (a) a first state inwhich reading/writing of the inserted optical disc is not available ifthe detected failure is a serious failure and (b) a second state inwhich reading/writing of the inserted optical disc is available butplayback of the video object is not available if the detected failure isa light failure; and a writing unit operable to write data onto theoptical disc when the state of the inserted optical disc is changed tothe second state.

[0011] With the above construction, when detecting a failure of theoptical disc relating to the playback of video data, therecording/playback apparatus changes the state of the optical disc to astate in which reading/writing of the optical disc is available, butplayback of the video object is not available. This state prevents therecording/playback apparatus from hanging up during a playback since theapparatus does not play back the video data. However, in thereading/writing available state, the apparatus can read or write datafrom/to the optical disc. This enables the apparatus to write a newvideo object without initializing the optical disc. As a result, theuser does not have to initialize the optical disc frequently.

[0012] The above object is also fulfilled by a recording/playbackapparatus for an optical disc on which a video object and managementinformation of the video object are recorded, the recording/playbackapparatus comprising: a detecting unit operable to detect a failure inthe management information recorded on the optical disc inserted in therecording/playback apparatus; a state transition control unit operableto change a state of the inserted optical disc to (a) a first state inwhich reading/writing of the inserted optical disc is not available ifthe detected failure is a serious failure, (b) a second state in whichreading/writing of the inserted optical disc is available but playbackof the video object is not available if the detected failure is a firstlight failure, and (c) a read only state if the detected failure is asecond light failure; a writing unit operable to write data onto theoptical disc if the state of the inserted optical disc is changed to thesecond state; and a playback unit operable to play back the video objectrecorded on the inserted optical disc if the state of the insertedoptical disc is changed to the read only state.

[0013] With the above construction, when detecting a failure that therecorded video data conforms to a DVD-VIDEO RECORDING standard that ishigher than the versions that the recording/playback apparatus can dealwith, the recording/playback apparatus changes the state of the opticaldisc to a read only state to preserve the data on the disc. Thisprevents the recording/playback apparatus from unnecessarily updatingand destroying the video data recorded on the DVD that conforms to aDVD-VIDEO RECORDING standard higher than those the apparatus can dealwith.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] These and the other objects, advantages and features of theinvention will become apparent from the following description thereoftaken in conjunction with the accompanying drawings which illustrate aspecific embodiment of the invention.

[0015] In the drawings:

[0016]FIG. 1 shows files and directories recorded on a DVD;

[0017]FIG. 2 shows a detailed construction of VOBs contained in AVfiles;

[0018]FIG. 3 shows the internal structure of the management file;

[0019]FIG. 4 shows relationships between VOBs and VOBIS;

[0020]FIG. 5 shows the construction of the TMAPI;

[0021]FIG. 6 shows relationships between TMAPIs and VOBUs;

[0022]FIG. 7 shows the internal structure of the management file;

[0023]FIG. 8 shows relationships between VOBs and CELLs contained in theORG_PGCI;

[0024]FIG. 9 shows how the CELLs shown in FIG. 7 are classified as PGs;

[0025]FIG. 10 shows the internal structure of the UD_PGCI table;

[0026]FIG. 11 shows an example of the PL defined for the VOBs and TMAPIsshown in FIG. 9;

[0027]FIG. 12 shows the internal structure of the TXTDT_MG table, theMNFI table, and the RTR_VMGI table;

[0028]FIG. 13 indicates how the location and size of each managementtable are determined from the start addresses (the M_AVFIT_SA throughthe MNFIT_SA) written on the VMGI_MAT and the effective lengths (theM_AVFIT_EA through the MNFIT_EA) written on the management tables;

[0029]FIG. 14 shows the internal structure of the recording/playbackapparatus;

[0030]FIGS. 15A to 15C show bit assignments of the VOB state flags, CELLstate flags, and TMAP state flags;

[0031]FIGS. 15D and 15E show bit assignments of the PG state flags andthe PL state flags;

[0032]FIG. 16 shows logical OR operations used to set the PG state flagsand the PL state flags;

[0033]FIG. 17 shows an example of a failure found in a VOB;

[0034]FIG. 18 shows how PGs or PLs referring to a VOB with a failure areset to “playback not available”;

[0035]FIG. 19 shows an example of a failure found in a TMAPI;

[0036]FIG. 20 shows how PGs or PLs referring to a TMAPI with a failureare set to “playback not available”;

[0037]FIG. 21 shows an example of a failure found in a CELL constitutinga PG;

[0038]FIG. 22 shows how a PG containing a CELL with a failure is set to“playback not available”;

[0039]FIG. 23 shows the bit assignment of the volume state flag;

[0040]FIG. 24 shows various disc states represented by the combinationof the volume state flag and the PG (PL) state flag;

[0041]FIG. 25 shows empirically known failures to be found in the datastructure conforming to the DVD-VIDEO RECORDING standard;

[0042]FIG. 26A shows an example of priority levels assigned to failures;

[0043]FIG. 26B shows how the disc state is determined from foundfailures in consideration of the priority levels shown in FIG. 26A;

[0044]FIG. 27 is a flowchart showing the procedure of the first checkprocess for the management file;

[0045]FIG. 28 is a flowchart showing the procedure of the second checkprocess;

[0046]FIG. 29 is a flowchart showing the procedure of the validity checkfor the VOB, VOBI, and TMAPI;

[0047]FIG. 30 is a flowchart showing the procedure of the third checkprocess for judging the validity of the ORG_PGCI;

[0048]FIG. 31 is a flowchart showing the procedure of judging thevalidity of the ORG_PGI;

[0049]FIG. 32 is a flowchart showing the procedure of judging thevalidity of the CELLI in a PG;

[0050]FIG. 33 is a flowchart showing the procedure of judging thevalidity of the UD_PGCI;

[0051]FIG. 34 is a flowchart showing the procedure of judging thevalidity of the UD_CELLI;

[0052]FIG. 35 is a flowchart showing the procedure of judging thevalidity of the TXTDT_MG; and

[0053]FIG. 36 is a flowchart showing the procedure of judging thevalidity of the MNFI.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0054] The following describes a recording/playback apparatus accordingto an embodiment of the present invention with reference to the attacheddrawings.

[0055]FIG. 1 shows files and directories recorded on a DVD. As shown inFIG. 1, the VIDEO_RTAV (RealTime recording Audio Video) directory isplaced immediately under the ROOT directory. Immediately under theVIDEO_RTAV directory, the AV file containing some VOBs and themanagement file containing a variety of pieces of management informationare placed.

[0056]FIG. 2 shows a detailed construction of VOBs contained in AVfiles. Each VOB (Video Object) is a program stream conforming to theISO/IEC13818-1 standard obtained by multiplexing video streams and audiostreams, and does not have a “program_end_code” at the end of it. Asshown in the upper-left block of FIG. 2, a video stream is a sequence ofa plurality of pieces of picture data. As shown in the second row of theupper-left block, the picture data sequence is divided into a pluralityof GOPs. Each GOP is further divided into a plurality of pieces of 2KB-data (packs). Also, as shown in the upper-right corner of FIG. 2, anaudio stream is divided into a plurality of pieces of 2 KB-data (packs).The video stream and audio stream are interleave-multiplexed in units of2 KBs to form the pack sequence shown in the first row in thelower-right corner of FIG. 2. As shown in FIG. 2, the pack sequence isdivided into a plurality of VOBUs (Video Object Units), and the VOB iscomposed of the plurality of VOBUs arranged in a time series. GOPscontain B-Pictures, P-Pictures, and I-Pictures. The B-Picture(Bidirectionally Predictive Picture) has been compressed in correlationwith pictures in the past and future directions. The P-Picture(Predictive Picture) has been compressed in correlation with pictures inthe past direction. The I-Picture (Intra Picture) has been compressedusing the spatial frequency characteristic of pictures in one frame.

[0057] As understood from FIG. 2, VOBU is a unit that is an interleavedsequence of (a) video packs forming at least one GOP and (b) audiopacks, where each GOP is composed of picture data to be played back forapproximately 0.4 to 1.0 seconds, and both video and audio packs conformto the MPEG standard.

[0058]FIG. 3 shows the internal structure of the management file. Asshown in FIG. 3, the management file is composed of an RTR_VMGI table(RTR_VMGIT), an M_AVFI table (M_AVFIT), an S_AVFI table (S_AVFIT), anORG_PGCI table (ORG_PGCIT), a UD_PGCI table (UD_PGCIT), a TXTDT_MG table(TXTDT_MGT), and an MNFI table (MNFIT). Of these, RTR_VMGIT throughORG_PGCIT contain information necessary for the playback and arereferred to as playback information tables, and UD_PGCIT through MNFITcontain information set by users during editing processes and arereferred to as user-edited information tables.

[0059] The M_AVFI (Motion AV File Information) table is used formanaging a VOB and is composed of, as indicated by the leader h3: aVOB_STI_Ns that indicates the number of VOB_STIs contained in theM_AVFIT; an M_AVFIT_EA (Effective Address) that shows the effectivelength of the M_AVFIT; VOB_STI (Stream Information) #1 . . . #K that isattribute information of the VOB; and an M_AVFI. The VOB STIs show videoattributes (coding mode, aspect ratio, NTSC/PAL, line21 information,etc.) of picture data contained in each VOB, and show audio attributes(coding mode, the number of channels, frequency, etc.) of audio datacontained in each VOB.

[0060] The M_AVFI (Motion AV File Information) is composed of, asindicated by the leader h4, VOBI #1 . . . #L. Each VOBI (Video ObjectInformation) is composed of, as indicated by the leader h5: a VOB_Typeindicating the type of the VOB; a VOB_Start_PTM indicating a playbackstart time when the first picture of the video stream of the VOB isplayed back; a VOB_End_PTM indicating a playback end time when the lastpicture of the video stream of the VOB is played back; a VOB_REC_TMindicating the date and time when the VOB started being recorded; aVOB_STIN being a pointer that points out one among the VOB_STI #1through #K that corresponds to the VOB, as indicated by the arrow Pr1;and a TMAPI being time map information of each VOBU constituting theVOB.

[0061]FIG. 4 shows relationships between VOBs and VOBIs. In FIG. 4, thecorrespondence between the VOBs and the VOBIs is indicated by theidentification numbers such as “#1” and “#2” attached to each VOBI andVOB. The playback start time and end time of each VOB are indicated bythe VOB_Start_PTM and VOB_End_PTM, respectively.

[0062] Now, the TMAPI will be described. FIG. 5 shows the constructionof the TMAPI. The TMAPI is composed of, as indicated by the leader hy3:a TMAP_GI (General Information); a TM_ENT #1 . . . #S; and a VOBU_ENT #1. . . #T.

[0063] Each VOBU_ENT is information corresponding to a VOBU. TheVOBU_ENT is composed of, as indicated by the leader hy4: a 1STREF_SZindicating the size of the first I-Picture of the corresponding VOBU; aVOBU_PB_TM indicating a time period (on the order of 0.4 through 1.0seconds) used for playing back the corresponding VOBU; and a VOBU_SZindicating the size of the corresponding VOBU. Even if each VOBU has adifferent size, it is possible to access a VOBU at a given playback timeby referring to the VOBU_ENT.

[0064] Each TM_ENT is information indicating the location of a timeentry at intervals of 10 seconds. The TM_ENT is composed of, asindicated by the leader hy5: a VOBU_ENTN indicating a VOBU containingthe time entry; a TM_DIFF indicating the offset time between the startof the VOBU indicated by the VOBU_ENTN and the time entry; and aVOBU_ADR indicating the offset data between the start of the VOB and thestart of the VOBU indicated by the VOBU_ENTN. The TM_ENT provideshigh-speed accesses at intervals of 10 seconds.

[0065] The TMAP_GI (Time Map General Information) is information usedformanaging the whole TMAPI and is composed of, as indicated by theleader hy6: a TM_ENT_Ns indicating the number of time entries set in theVOB; a VOBU_ENT_Ns indicating the number of VOBU_ENTs contained in theTMAPI; a TM_OFS indicating the offset between the start of the VOB andone time entry; and an ADR_OFS indicating the offset between the startof the AV file and the start of the VOB.

[0066]FIG. 6 shows relationships between TMAPIs and VOBUs. Thecorrespondence between the playback time and the size for each VOBU isshown by a combination of the VOBU_PB_TM (PB_TM in FIG. 6) and theVOBU_SZ. The TM_DIFF in the TM_ENT indicates how many seconds after aplayback start of the VOBU the time entry is reached. The TMAPI with theabove construction allows the VOBU corresponding to a given time code tobe identified.

[0067] Up to now the M_AVFIT has been described. From now on, theS_AVFIT and the ORG_PGCIT contained in the management file will bedescribed with reference to FIG. 7. FIG. 7 shows the internal structureof the management file. FIG. 7 differs from FIG. 3 in that the internalstructure of the ORG_PGCI table is shown.

[0068] The S_AVFI (Still AV File Information) table is used to writevarious information concerning VOBs that are recorded on the DVD andshould be played back as still pictures.

[0069] The ORG_PGCI (Original Program Chain Information) table definesdetails of the Original_Program Chain that is a playback route unique tothe DVD. The ORG_PGCIT is composed of, as indicated by the leader h6: anOPG_PGCI_EA (Effective Address) indicating the effective length of theOPG_PGCI table; a PG_Ns indicating the number of Programs (PGs)contained in the ORG_PGC, where the Programs are units of playback; aCI_SRP_Ns indicating the number of search pointers for the CELLI (CI);an ORG_PGI #1 . . . #M which is information concerning each of aplurality of PGs contained in the ORG_PGC; an ORG_CI_SRP #1 . . . #Nbeing search pointers for a plurality of CELLIs; and an ORG_CELLI #1 . .. #N.

[0070] The ORG_CELLI is information on the CELLs constituting theORG_PGC. Each CELL is a playback section constituting the ORG_PGC. Morespecifically, the ORG_CELLI contains (a) a pointer VOBI_SRPN specifyingone among a plurality of VOBIs contained in the M_AVFIT that correspondsto the CELLI and (b) a CELL_Start_PTM and a CELL_End_PTM which are apair of time codes showing a section in the VOB specified as a playbacksection (referred to as CELL).

[0071]FIG. 8 shows relationships between VOBs and CELLs contained in theORG_PGCI. In FIG. 8, the correspondence between the CELLs and the VOBIsis indicated by the VOBI_SRPN. A pair of the CELL_Start_PTM (in FIG. 8,C_S_PTM) and the CELL_End_PTM (in FIG. 8, C_E_PTM) contained in the CELLare converted into two VOBU addresses by referring to the TMAP. As aresult, a section of a VOB is specified as a CELL.

[0072] The ORG_PGI is composed of, as indicated by the leader h7 shownin FIG. 7: an IT_TXT_SRPN specifying anIT_TXTI that corresponds to thePG, among a plurality of IT_TXTIs contained in the TXTDT_MG; and a C_Nsindicating the number of CELLIs contained in the PG.

[0073]FIG. 9 shows how the CELLs shown in FIG. 7 are classified as PGs.As shown in FIG. 9, the CNs contained in the PGI indicates a series ofCELLs belonging to PG #1, among the CELLs #1 through #2 contained in theORG_PGCI, and a series of CELLs belonging to PG #2. Further, theIT_TXT_SRPN contained in the PG indicates the IT_TXTI that includes textdata corresponding to the PG.

[0074] Up to now, the ORG_PGCI has been described. Now, the internalstructure of the UD_PGCI will be described with reference to FIG. 10.

[0075] The UD_PGCIT (User Defined Program Chain Table) is composed of,as indicated by the leader h9: a UD_PGCIT_EA indicating the effectivelength of the UD_PGCIT; a UD_PGCI_SRP_Ns indicating the number ofUD_PGCI_SRPs; a UD_PGCI_SRP #1 . . . #K each of which is a searchpointer for a UD_PGCI; and user-defined PGC information UD_PGCI #1 . . .#K. The UD_PGCI is information specifying user-defined playback routeinformation referred to as a PlayList (PL). The UD_PGCI is composed of,as indicated by the leader h10: a CELLI_SRP_Ns indicating the number ofUD_CI_SRPs; a UD_CI_SRP #1 . . . #M each of which is a search pointerfor a UD_CELLI (UD_CI); and a UD_CELLI (User Defined CELL Information)#1 . . . . #M defining a playback CELL constituting the PL. The CELLI inthe UD_PGCI has the same construction as the CELLI in the ORG_PGI and iscomposed of: a VOBI_SRPN being a search pointer for a VOBI of a VOBcorresponding to the CELL; a time code CELL_Start_PTM indicating a startpoint of the CELL; and a time code CELL_End_PTM indicating an end pointof the CELL.

[0076]FIG. 11 shows an example of the PL defined for the VOBs and TMAPIsshown in FIG. 9. As shown in FIG. 11, CELL #1 constituting PL #1specifies TMAP #1 contained in VOBI #1. Further, a pair of theCELL_Start_PTM (in FIG. 11, C_S_PTM) and the CELL_End_PTM (in FIG. 11,C_E_PTM) indicates a section of VOB #1 that corresponds to CELL #1constituting PL #1. Further, the IT_TXT_SRPN contained in the PLindicates the IT_TXTI that includes text data corresponding to the PL.

[0077] Now, the contents of the TXTDT_MG table, the MNFI table, and theRTR_VMGI table will be described with reference to FIG. 12.

[0078] The TXTDT_MG (Text Data Manager) table is composed of, asindicated by the leader h12: a TXTDT_MG_EA indicating the effectivelength of the TXTDT_MG; an IT_TXT_SRP_Ns (Item Text Search PointerNumbers) indicating thenumber of the IT_TXT_SRPs; an IT_TXT_SRP (ItemText Search Pointer) #1 . . . #K that are search pointers for eachIT_TXT; and an item text IT_TXT #1 . . . #K. Each IT_TXT_SRP is composedof, as indicated by the leader h14: an IT_TXT_SA (Start Address) beingthe start address of IT_TXT; An IT_TXT_SZ being the size of IT_TXT; andIT_TXT being a character sequence representing, for example, a programname or a scene name defined by the user.

[0079] The MNFI table is composed of, as indicated by the leader h13: anMNFI_EA indicating the effective length of the MNFIT; an MNFI_Nsindicating the number of MNFIs; an MNFI #1 . . . #L in which informationunique to each recording/playback apparatus is written. The informationunique to each recording/playback apparatus is, for example, pointerinformation used to write an entry point concerning a thumbnail image oran entry point of thumbnail.

[0080] The RTR_VMGI (Real Time Recording Video Management GeneralInformation) table is composed of, as indicated by the leader h20: aVMGI_MAT (Real Time Recording Video Management General Information MapTable); a PL_SRP_Ns indicating the number of the playlist searchpointers set for the DVD-RAM; and a PL_SRP #1 . . . #K. The VMGI_MAT iscomposed of, as indicated by the leader h21: an RTR_VMGI_EA indicatingthe effective length of the RTR_VMGI table; and an M_AVFIT_SA, anS_AVFIT_SA, an ORG_PGCI_SA, an UD_PGCIT_SA, a TXTDT_MG_SA, and anMNFIT_SA which are the start addresses of the management tables.

[0081] The PL_SRP is composed of, as indicated by the leader h22: a PGCNindicating a user-defined PGC corresponding to the PL; and anIT_TXT_SRPN being a pointer specifying a text corresponding to the PL.

[0082]FIG. 13 indicates how the location and size of each managementtable are determined from the start addresses (the M_AVFIT_SA throughthe MNFIT_SA) written on the VMGI_MAT and the effective lengths (theM_AVFIT_EA through the MNFIT_EA) written on the management tables. Theranges indicated by the sign “{” in FIG. 13 indicate the locations andsizes of the management tables determined from the start addresses andthe effective lengths. The start addresses (the M_AVFIT_SA through theMNFIT_SA) of the management tables written on the VMGI_MAT are each anoffset from the start of the management file to the start of eachmanagement table. The effective lengths (the M_AVFIT_EA through theMNFIT_EA) of the management tables are each an offset from the start tothe end of the management table, where the start is “0”. Accordingly,the end address of each management table is obtained by adding theeffective length written on the management table to the start address ofthe management table written on the VMGI_MAT of the RTR_VMGI.

[0083] If the start address and the effective length are correct, theobtained end address of a management table is equal to or smaller thanthe start address of the next management table. If the start address andthe effective length are incorrect, the obtained end address is greaterthan the start address of the next management table, meaning that thesemanagement tables overlap.

[0084] Up to now, the data structure of the DVD has been described. Fromnow on, the internal structure of the recording/playback apparatus willbe described. FIG. 14 shows the internal structure of therecording/playback apparatus. As shown in FIG. 14, therecording/playback apparatus includes a DVD drive 1, a flag holding unit2, a flag holding unit 3, a flag setting unit 4, a flag holding unit 5,a disc state management unit 6, a recording/playback/editing unit 7(which contains a disc reading unit 8, a semiconductor memory 9, an MPEGdecoder 10, and MPEG encoder 11, an editing unit 12, and a disc writingunit 13), and a validity check unit 14.

[0085] The DVD drive 1 sets a DVD, to/from which data is written or readand played back, to the state in which the DVD can be accessed.

[0086] The flag holding unit 2 holds: a plurality of VOB state flagsindicating the state of a plurality of VOBs recorded on the DVD; aplurality of CELL state flags indicating the state of a plurality ofCELLs contained in the management file; and a plurality of TMAP stateflags indicating the state of a plurality of TMAPIs. Each VOB state flagindicates whether a corresponding VOB can be played back or not. EachCELL state flag indicates whether a corresponding CELL can be playedback or not. Each TMAP state flag indicates whether a correspondingTMAPI can be edited or not. These VOB, CELL, and TMAP state flags havebit assignments common to each other, as shown FIGS. 15A to 15C. Eachflag consists of 2 bits. When the first bit is “0”, it indicates thatthe object can be played back; and when the first bit is “1”, itindicates that the object cannot be played back. When the second bit is“0”, it indicates that the object can be edited; and when the second bitis “1”, it indicates that the object cannot be edited.

[0087] The flag holding unit 3 holds: a plurality of PG state flagsindicating the state of a plurality of PGs recorded on the DVD; and aplurality of PL state flags indicating the state of a plurality of PLsrecorded on the DVD. FIG. 15D shows the bit assignment of the PG stateflag. As shown in FIG. 15D, the PG state flag consists of 2 bits. Whenthe first bit is “0”, it indicates that the object can be played back;and when the first bit is “1”, it indicates that the object cannot beplayed back. When the second bit is “0”, it indicates that the objectcan be edited; and when the second bit is “1”, it indicates that theobject cannot be edited. FIG. 15E shows the bit assignment of the PLstate flag. The bit assignment is the same as that of the PG state flagshown in FIG. 15D.

[0088] The flag setting unit 4 sets the PG state flags by implementingthe logical OR operation between the CELL state flags corresponding toall CELLIs specified by the CNs contained in the PGI, the VOB stateflags corresponding to all VOBs specified by the VOBI_SRPN of theseCELLIs, and the TMAP state flags corresponding to the TMAPIscorresponding to these VOBs. Also, the flag setting unit 4 sets the PLstate flags by implementing the logical OR operation between the CELLstate flags corresponding to all CELLIs contained in the PLs, the VOBstate flags corresponding to all VOBs specified by the VOBI_SRPN ofthese CELLIs, and the TMAP state flags corresponding to the TMAPIscorresponding to these VOBs. Now, how the PG and PL state flags are setin the case of PG #1, PG #2, and PL #1 shown in FIG. 11 will bedescribed. As shown in FIG. 11, the PGCI contains two CELLs #1 and #2.It is supposed here that the CELL state flags for these CELLs are all“00”. It is also supposed here that the VOBI_SRPNs of these CELLIsspecify VOBs #1 and #2, that the VOB state flags corresponding to theseVOBs are “00” and “01”, that VOBs #1 and #2 correspond to TMAPIs #1 and#2, and that the TMAP state flags corresponding to these TMAPIs are “00”and “00”. The PG state flags and the PL state flag corresponding to PG#1, PG #2, and PL #1 are obtained by implementing the logical ORoperations shown in FIG. 16. The results of these logical OR operationsare as follows.The  PG  state  flag  #1  for  PG  #1 = 00⋃00⋃01 = 01The  PG  state  flag  #2  for  PG  #2 = 00⋃00⋃00 = 00The  PL  state  flag  #1  for  PL  #1 = 00⋃00⋃00⋃00⋃01⋃00   = 01

[0089] As understood from this, when a failure is found in a VOB asshown in FIG. 17 and when the VOB state flag corresponding to thefailure VOB is set to “Play NG” that indicates “playback not available”,PG #1 and PL #1 referring to the VOB are set to “Play NG” as shown inFIG. 18.

[0090] Similarly, when a failure is found in a TMAPI as shown in FIG. 19and when the TMAP state flag corresponding to the failure TMAPI is setto “Edit NG” that indicates “editing not available”, PG #1 and PL #1referring to the TMAPI are set to “Edit NG” as shown in FIG. 20.

[0091] On the other hand, when a failure is found in a CELL contained ina PG or a PL, only the PG or the PL containing the failure CELL are setto “Play NG”, and other PGs and PLs not containing the CELL are not setso. That is to say, the failure does not affect the other PGs and PLs.More specifically, when a failure is found in the CELLs constituting PG#1 as shown in FIG. 21, only PG #1 is set to “Play NG” and PG #2 and PL#1 are set to “Play OK” that indicates “playback available”, notaffected by the failure. When a failure is found in a VOB or a TMAPI,all PGs and PLs referring to the VOB or the TMAPI are set to “Play NG”or “Edit NG”. This prevents mulfunctions of the playback process and theediting process for PGs and PLs based on the found failure.

[0092] The flag holding unit 5 holds a plurality of volume state flagsindicating the state of management files recorded on the DVD. FIG. 23shows the bit assignment of the volume state flag. As shown in FIG. 23,the volume state flag consists of 2 bits and indicates “Not Open” whenthe bits are “11”, “Read Only” when the bits are “01”, and “Normal” whenthe bits are “00”, where “Not Open” indicates that data cannot be readnor written from/to the DVD inserted in the DVD drive 1, “Read Only”indicates that the DVD is in the read-only state, and “Normal” indicatesthat data can be read or written from/to the DVD.

[0093] The disc state management unit 6 manages the disc state regardingthe state indicated by the volume state flag as the main state, and thestate indicated by the PG (PL) state flag as the sub state. FIG. 24shows various disc states represented by the combination of the volumestate flag and the PG (PL) state flag. As shown in FIG. 24, there are 6disc states: (1) “Not Open” where data cannot be read nor writtenfrom/to the DVD; (2) “ReadOnly” where PGs (PLs) can be played back; (3)“ReadOnly” where the PGs (PLs) cannot be played back; (4) “Normal” wheredata can be read and written from/to the DVD and PGs (PLs) can be playedback and edited; (5) “Normal” where data can be read and written from/tothe DVD, PGs (PLs) can be played back but cannot be edited; and (6)“Normal” where PGs (PLs) cannot be played back nor edited. When afailure is found in the DVD, the disc state becomes one of (1), (2),(3), (5), and (6) indicated by the triangle mark, depending on theseriousness of the failure.

[0094] The recording/playback/editing unit 7 executes the reading andwriting data from/to the DVD inserted in the DVD drive 1 and executesthe playback and editing of PGs and PLs recorded on the DVD, dependingon the disc state managed by the disc state management unit 6. Moreparticularly, the recording/playback/editing unit 7 contains the discreading unit 8 that reads a VOB and the management file when the volumestate flag is set to “Normal” or “ReadOnly”, the semiconductor memory 9that stores the management file read from the DVD, the MPEG decoder 10that decodes the VOB read from the DVD and outputs an image signal andan audio signal when the PG state flag or PL state flag is set to “PlayOK”, the MPEG encoder 11 that obtains a VOB by encoding an image signaland an audio signal input from outside the apparatus when the volumestate flag is set to “Normal”, the editing unit 12 that edits themanagement file stored in the semiconductor memory 9 in accordance witha user's instruction when the PG state flag is set to “Edit OK”, and thedisc writing unit 13 that writes (1) the edited management file and (2)the VOB encoded by the MPEG encoder 11 onto the DVD when the volumestate flag is set to “Normal”.

[0095] The validity check unit 14 checks whether the data structure ofthe management file and VOBs recorded on the DVD are valid. Here, beingvalid means that the data structure of the DVD conforms to the DVD-VIDEORECORDING standard of a version to which the recording/playbackapparatus is adaptable. As a result, the data structure is judged asinvalid not only when the DVD has a portion violating the DVD-VIDEORECORDING standard but when the DVD conforms to the DVD-VIDEO RECORDINGstandard of a version higher than the version to which therecording/playback apparatus is adaptable.

[0096]FIG. 25 shows empirically known failures to be found in the datastructure conforming to the DVD-VIDEO RECORDING standard. The managementfile failures (1) and (2) are thought to be found in the data structureof the management file. The CELL failures (3), (4), and (5) are thoughtto be found in the CELLIs. The TMAP failure (6) is thought to be foundin the TMAPIs. The VOB failure (7) is thought to be found in the VOBs.These failures are empirically expected to be found in the DVD. Themanagement file failure (1) means that the start address of the M_AVFITor the ORG_PGI, which are what is called playback information tables, isincorrect. The management file failure (2) means that (a) the startaddress of any of the UD_PGCI through the MNFIT is incorrect, (b) thetable has been overwritten, or (c) the number of elements such as VOBs,MNFIS, PGs, PLs, CIs, or TXTs is out of specifications. The CELL failure(3) means that a VOB specified by a CELLI constituting a PG overlapswith a VOB specified by another CELLI constituting a PG. The CELLfailure (4) means that a CELLI that does not refer to a VOB has beenrecorded. The CELL failure (5) means that a CELLI with incorrect C_S_PTMor C_E_PTM has been recorded. The TMAP failure (6) means that a TMAPIwith incorrect VOB address, VOBU address, or VOBU number has beenrecorded. The VOB failure (7) means that (a) a VOB address is incorrect,(b) no corresponding STI is found, (c) a pair of a VOB_Start PTM and aVOB_End_PTM is incorrect, or (d) a video or audio stream constituting aVOB has been encoded in an out-of-spec coding mode.

[0097] It should be noted here that the incorrect VOB address, VOBUaddress, and VOBU number mean, for example, that a VOBU address ornumber has been replaced with the preceding or succeeding one, that aVOBU address exceeds the file size, or that a VOBU number is “0”.

[0098] The above failures are assigned with priority levels as shown inFIG. 26A. The disc state is determined in consideration of the prioritylevels. The highest priority level is given to the management filefailure (1). The second priority level is given to the management filefailure (2) and the CELL failures (3) and (4). The third priority levelis given to the CELL failure (5), the TMAP failure (6), and the VOBfailure (7).

[0099] When a plurality of failures is found, the disc state isdetermined based on the highest priority level among those assigned tothe found failures. In other words, the disc state is determined basedon the CELL failure (5), the TMAP failure (6), or the VOB failure (7)when no failure with a higher priority level is found. FIG. 26B is atable that shows how the disc state is determined from found failures inconsideration of the priority levels shown in FIG. 26A. The table shownin FIG. 26B indicates that the volume state flag is set to “NotOpen”when the management file failure (1) with the first priority level isfound, that the volume state flag is set to “ReadOnly” when any of themanagement file failure (2), and the CELL failures (3) and (4) with thesecond priority level is found, and that the CELL state flag, the TMAPstate flag, or the VOB state flag is set to “Play NG”, “Edit NG”, or“Play NG” when the CELL failure (5), the TMAP failure (6), or the VOBfailure (7) with the third priority level is found, respectively. Itshould specifically be noted in FIG. 26B that when any of the CELLfailure (5), the TMAP failure (6), and the VOB failure (7) is found andnone of the management file failures (1) and (2) and the CELL failures(3) and (4) is found, the volume state flag is not affected. That meanswhen only any of the CELL failure (5), the TMAP failure (6), and the VOBfailure (7) is found, reading and writing data from/to the DVD can beperformed without restriction.

[0100] The validity check unit 14 includes (a) a program in which theprocedures shown as flowcharts in FIGS. 27 through 36 are written and(b) a general-purpose microcomputer for executing the procedures. Now,the procedures of the validity check unit 14 will be described withreference to the flowcharts.

[0101]FIG. 27 is a flowchart showing the procedure of the first checkprocess for the management file. In step S1, all flags are cleared tozero, then in steps S2 through S6, it is judged whether the startaddress of each table exceeds the management file effective lengthRTR_VMG_EA. In steps S2 and S3, it is judged whether the management filefailure (1) exists. In steps S4 through S6, it is judged whether themanagement file failure (2) exists.

[0102] When it is judged that the M_AVFIT_SA or the ORG_PGCIT_SA exceedsthe RTR_VMG_EA (“YES” in step S2 or S3), the control moves to step S10where the volume state flag is set to “NotOpen”, without reading themanagement file onto the memory.

[0103] When it is judged that the UD_PGCI_SA, TXTDT_MG_SA, or MNFIT_SAexceeds the RTR_VMG_EA (“YES” in step S4, S5, or S6), the control movesto step S7, S8, or S9, respectively, and the volume state flag is set to“ReadOnly”, and a table other than the tables with a failure(UD_PGCI_SA, TXTDT_MG_SA, and MNFIT_SA) is read onto the semiconductormemory 9 to end the first check process and move to the second checkprocess.

[0104]FIG. 28 is a flowchart showing the procedure of the second checkprocess. The second check process checks the validity of the M_AVFIT. Instep S11, the size of the M_AVFIT is calculated and the obtained size isset as a variable “SIZE”. Here, the size of the M_AVFIT is calculatedusing the size of each table constituting theM_AVFIT and the number ofelements in each table. The size of each table is defined in theDVD-VIDEO RECORDING standard. The number of elements in each table ismanaged by each table. For example, the size of the VOB_STI table is 60bytes, and the number of elements is indicated by the VOB_STI_Ns of theM_AVFIT. Using these information, the size of theM_AVFIT is calculatedas follows. $\begin{matrix}{{SIZE} = \quad {{2\left( {= {{size}\quad {of}\quad {VOB\_ STI}{\_ Ns}}} \right)} + {4\left( {= {{size}\quad {of}\quad {M\_ AVFIT}{\_ EA}}} \right)} +}} \\{\quad {{60\left( {= {{size}\quad {of}\quad {VOB\_ STI}}} \right) \times {VOB\_ STI}{\_ Ns}} +}} \\{\quad {\sum\left( {{sizes}\quad {of}\quad {VOBIs}} \right)}}\end{matrix}$

[0105] The reason why the sum of the VOBI sizes is obtained using Σ isthat each VOB has a different time map size. After calculating the sizeof the M_AVFIT, steps S12 through S14 are performed for the M_AVFIT. Instep S12, it is judged whether it is true that the M_AVFIT_EA in theM_AVFIT is not equal to “SIZE”. TheM_AVFIT_EAisanoffset fromthe start oftheM_AVFIT to the end of it, where the start is “0”. That is to say, theM_AVFIT_EA is the size of the M_AVFIT. Accordingly, the M_AVFIT_EAshould be equal to “SIZE”.

[0106] In step S13, it is checked whether the M_AVFIT overlaps with thenext table. The checking is made by judging whether the sum of “SIZE”obtained in step S11 and the M_AVFIT_SA in the RTR_VMGI is larger thanthe ORG_PGCI_SA in the RTR_VMGI.

[0107] In step S14, it is checked whether the number of VOBIs(M_AVFIT.VOBIs) managed by the M_AVFIT exceeds the highest value withinspecifications. When it is judged as “YES” in step S12, S13, or S14(i.e., the condition is not satisfied), the control goes to step S19 orS20, where the volume state flag is set to “ReadOnly”. Also, in stepS20, the M_AVFIT.VOBIs is set to the highest value within the DVD-VIDEORECORDING standard, and the management file with the M_AVFIT.VOBIs isread onto the semiconductor memory 9.

[0108] In the present example, it is supposed that no still picture isrecorded. As a result, the flowchart shown in FIG. 28 shows a procedurein the case where the table next to the M_AVFIT is the ORG_PGCI. If astill picture was recorde, the address used in the comparison in stepS13 would be the S_AVFIT_SA in the RTR_VMGI instead of the ORG_PGCI inthe RTR_VMGI.

[0109] When the above three conditions are satisfied, the control movesto a loop process composed of steps S15 through S18. The number of loopexecutions is indicated by a variable “VobNo”. In step S15, “VobNo” iscleared to zero. In step S16, “VobNo” is incremented by “1” indicatingthat the loop is executed once. The loop terminates when it is judged instep S17 that “VobNo” exceeds the M_AVFI.VOBIs. When the loopterminates, the third check process is performed. The validity check forthe VOB [VobNo] is detailed in the flowchart shown in FIG. 29.

[0110] The flowchart of FIG. 29 includes a plurality of judgment stepsS21 through S28. The VOB, VOBI, and TMAPI specified by VobNo are judgedas valid only after all the judgment steps are cleared. The steps S21through S25 are performed to judge whether the VOB failure (7) exists.The steps S26 through S28 are performed to judge whether the TMAPfailure (6) exists.

[0111] In step S21, it is judged whether the start address of the VOBI[VobNo] is correct. In step S22, it is judged whether a VOB_STI referredto by the VOBI [VobNo] exists. In step S23, it is judged whether a videocoding mode specified by the VOB_STI conforms to the standard. In stepS24, it is judged whether an audio coding mode specified by the VOB_STIconforms to the standard. In step S25, it is judged whether theVOB_Start_PTM and the VOB_End_PTM specified by the VOB_STI satisfy thecondition “VOB_Start_PTM<VOB_End_PTM”. When any of the above conditionsis not satisfied, the control moves to step S29, where the VOB stateflag [VobNo] is set to “Play NG”.

[0112] In step S26, it is judged whether the address of the VOB [VobNo]is incorrect. In step S27, it is judged whether the VOBU address in theTMAPI contained in the VOBI [VobNo] is incorrect. In step S28, it isjudged whether the VOBU_ENT number in the TMAPI contained in the VOBI[VobNo] is incorrect. When any of the above conditions is not satisfied,the control moves to step S30, where the TMAP state flag [VobNo] is setto “Edit NG”.

[0113] After the processes shown in FIGS. 28 and 29 are complete, thethird check process whose flowchart is shown in FIG. 30 is performed.The third check is performed to judge whether the ORG_PGCI is valid. Instep S31, the size of the ORG_PGCI is calculated and the obtained sizeis set as a variable “SIZE”. The control then moves to the steps S32through S35 for a plurality of judgments. These judgments are aimed tocheck whether the management file failure (2) exists. In step S32, it isjudged whether it is true that the ORG_PGCI_EA in the ORG_PGCI is notequal to the variable “SIZE”. Instep S33, it is judged whether theORG_PGCIT overlaps with the UD_PGCIT. In step S34, it is judged whetherthe PG_Ns exceeds the highest value within specifications. In step S35,it is judged whether the CI_SRP_Ns exceeds the highest value withinspecifications. When any of the conditions is not satisfied, the controlgoes to steps S42 through S44, where the volume state flag is set to“ReadOnly”, and in steps S44 and S45, the PG_Ns and the CI_SRP_Ns areset to the highest value within specifications, and the management filewith the PG_Ns and the CI_SRP_Ns is read onto the semiconductor memory9.

[0114] Steps S36 through S45 constitute a loop, where the number of loopexecutions is indicated by a variable “pNo”. The variable pNo isinitialized in step S36. In step S37, “pNo” is incremented by “1”indicating that the loop is executed once. The loop terminates when itis judged that “pNo” exceeds the PG_Ns. In step S40, the number of CELLsindicated by “pNo” is added to the ORG_CELLs that is initialized in stepS36 together with “pNo”, and the ORG_CELLs is set to the sum of thesevalues. In step S41, the ORG_CELLs is compared with the CI_SRP_Ns. Thisis the first object of this loop process. When it is not judged in stepS41 that the ORG_CELLs is equal to the CI_SRP_Ns, the control goes tostep S45, where “pNo” is substituted for the PG_Ns, then the controlgoes to the fourth check process.

[0115] The second object of the loop process is to check whether theORG_PGI indicated by “pNo” is valid, which is achieved in step S39.

[0116] This validity check for the ORG_PGI is detailed in the flowchartshown in FIG. 31.

[0117] In the flowchart shown in FIG. 31, steps S51 through S56constitute a loop, where the number of loop executions is indicated by avariable “cNo”. The variable cNo is initialized in step S51. Instep S52,“cNo” is incremented by “1” indicating that the loop is executed once.The loop terminates when it is judged in step S53 that “cNo” exceeds theORG_PGI [pNo] C_Ns. The control also exits from the loop when it isjudged in step S55 that the sum of the ORG_CELLs and “cNo” is equal tothe CI_SRP_Ns. It should be noted here that in this case, “cNo” is setto the ORG_PGI [pNo].C_Ns. Each time it is judged negatively in stepS55, the control returns and it is judged whether the CELLI in theORG_PGI [pNo] indicated by “cNo” is valid, until a positive judgment ismade in step S53. After the PG check is over in this loop, the controlgoes to step S57, where the flag setting unit 4 sets the PG state flag[cNo] based on the VOB state flags, the TMAP state flags, and the CELLstate flags.

[0118] The validity check of the CELLI is detailed in the flowchartshown in FIG. 32. The flowchart contains judgment steps S61, S62, andS63 to check whether respective conditions are satisfied. In step S61,it is judged whether the CELL failure (4) exists. In step S62, it isjudged whether the CELL failure (3) exists. In step S63, it is judgedwhether the CELL failure (5) exists. When it is judged in step S61 thatno VOB referred to by the CELL [cNo] exists, the control goes to stepS64, where the volume state flag is set to “ReadOnly”, and the CELLstate flag [cNo] is set to “Play NG”. When it is judged in step S62 thatthe CELL [cNo] overlaps another CELL, the control goes to step S65,where the volume state flag is set to “ReadOnly”. When it is judged instep S63 that any of the conditions CELL_Start_PTM<VOB_Start_PTM,CELL_End_PTM<VOB_Start_PTM, VOB_End_PTM<CELL_Start_PTM,VOB_End_PTM<CELL_End_PTM, CELL_End_PTM<CELL_Start_PTM is satisfied, thecontrol goes to step S66, where the CELL state flag [cNo] is set to“Play NG”.

[0119] Now, the fourth check process will be described. This checkprocess is executed to check whether the UD_PGCI is valid in accordancewith the flowchart shown in FIG. 33. In step S71, it is judged whetherit is true that the UD_PGCI_SA is not “0”. In step S72, the size of theUD_PGCI is calculated and the variable “SIZE” is set to the calculatedsize. Judgments are then made in steps S73 through S75. Through thesesteps, it is judged whether the management file failure (2) exists. Instep S73, it is judged whether it is true that the UD_PGCI_EA is not“SIZE”. The step S74 is performed to check whether the TXTDT_MG overlapsthe UD_PGCIT. In step S75, it is judged whether the PL_SRP_Ns indicatingthe PL_Ns exceeds the highest value within specifications.

[0120] When any of the above conditions is not satisfied, the controlgoes to step S80 or S81, where the volume state flag is set to“ReadOnly”, and in step S81, the RTR_VMGI.PL_SRP_Ns is set to thehighest value within specifications, and the management file with theRTR_VMGI.PL_SRP_Ns is read onto the semiconductor memory 9.

[0121] Steps S76 through S79 constitute a loop, where the number of loopexecutions is indicated by a variable “pNo”. The variable pNo isinitialized in step S76. In step S77, “pNo” is incremented by “1”indicating that the loop is executed once. The loop terminates when itis judged in step S78 that “pNo” exceeds the RTR_VMGI.PL_SRP_Ns. Theobject of this loop is achieved in step S78, where it is checked whetherthe UD_CELLI indicated by “pNo” is valid.

[0122] The validity check for the UD_CELLI is executed in accordancewith the flowchart shown in FIG. 34. Steps S82 through S88 constitute aloop, where the number of loop executions is indicated by a variable“cNo”. The variable cNo is initialized in step S82. Instep S83, “cNo” isincremented by “1” indicating that the loop is executed once. The loopterminates when it is judged in step S83 that “cNo” exceeds theCI_SRP_Ns of the UD_PGCI. The object of this loop is achieved in stepsS85 and 86, where it is checked whether the CELL [cNo] satisfies certainconditions.

[0123] In step S85, it is judged whether it is true that the CELLI [cNo]does not refer to any VOB. When it is judged positively in step S85, thecontrol goes to step S87, where the volume state flag is set to“ReadOnly”, and the CELL state flag [cNo] is set to “Play NG”. When itis judged in step S86 that any of the conditionsCELL_Start_PTM<VOB_Start_PTM, CELL_End_PTM<VOB_Start_PTM,VOB_End_PTM<CELL_Start_PTM, VOB_End_PTM<CELL_End_PTM,CELL_End_PTM<CELL_Start_PTM is satisfied, the control goes to step S88,where the CELL state flag [cNo] is set to “Play NG”. After the loop isrepeated for checking as many times as there are CELLs that constitutethe PL, the control goes to step S89, where the flag setting unit 4 setsthe PL state flag based on the VOB state flags, the TMAP state flags,and the CELL state flags.

[0124] From now on, the seventh check process will be described withreference to FIG. 35. FIG. 35 is a flowchart showing the procedure ofchecking the TXTDT_MG, which is an ITEM_TXT table. In step S91, it isjudged whether the TXTDT_MG_SA, which is the start address of the TXTDT,is “0”. In step S92, it is judged whether the IT_TXT_SRPs exceeds thehighest value within specifications. When it is judged positively instep S92, the control goes to step S99, where the volume state flag isset to “ReadOnly”, the IT_TXT_SRP_Ns is set to the highest value withinspecifications, and the management file with the IT_TXT_SRP_Ns is readonto the semiconductor memory 9. Steps S93 through S98 constitute aloop, where the number of loop executions is indicated by the IT_TXT_No.The IT_TXT_No is initialized in step S93. In step S94, the IT_TXT_No isincremented by “1” indicating that the loop is executed once. The loopterminates when it is judged in step S95 that the IT_TXT_No exceeds theIT_TXT_SRP_Ns.

[0125] In step S96, the IT_TXT [IT_TXT_No] is obtained using an addressindicated by the IT_TXT_SRP [IT_TXT_No]. In step S97, the end address“ADDR” of the IT_TXT [IT_TXT_No] is obtained by adding up theIT_TXT_SIZE and the IT_TXT_SA managed by the IT_TXT [IT_TXT_No]. In stepS98, it is judged whether the TXTDT_MG_EA managed in the TXTDT_MGexceeds “ADDR”. The above sequence of steps is executed each time theIT_TXT_No is incremented.

[0126] When it is judged negatively in step S98, the control goes tostep S100, where the IT_TXT_No is decremented by “1”. In step S101, eachPGI or PL_SRP that has the IT_TXT_SRPN greater than the IT_TXT_No isamended so as not to refer to the IT_TXT, and the management file withthe the IT_TXT_No is read onto the semiconductor memory 9.

[0127] Lastly, the eighth check process will be described with referenceto FIG. 36. FIG. 36 is a flowchart showing the procedure of checking theMNFI. In step S111, it is judged whether it is true that the MNFI_SA isnot “0”. In step S112, it is judged whether the MNFI_Ns exceeds thehighest value within specifications. When it is judged negatively instep S111, the whole process represented by the flowcharts is completed.When it is judged positively in step S112, the control goes to stepS118, where the volume state flag is set to “Readonly”, the MNFI_Fs isset to the highest value within specifications, and the management filewith the MNFI_Fs is read onto the semiconductor memory 9. Steps S113through S120 constitute a loop, where the number of loop executions isindicated by the MNFI_No. The MNFI_No is initialized in step S113. Instep S120, the MNFI_No is incremented by “1” indicating that the loop isexecuted once. The loop terminates when it is judged in step S114 thatthe MNFI_No exceeds the MNFI_Ns. The object of the loop is achieved byjudgment steps S115 and S116.

[0128] In step S115, it is judged whether the MNFI_SRP [MNFI_No]indicating the start address of the MNFI [MNFI_No] is smaller than theMNFIT_EA managed in the MNFIT. In step S116, it is judged whether theMNFI_SRP [MNFI_No] is greater than the ADDR_A. When it is judgednegatively in step S115 or step S116, the control Exits the loop andgoes to step S119, where all MNFITs are deleted, and the management fileafter this amendment is read onto the semiconductor memory 9.

[0129] It should be noted here that the address “ADDR_A” is obtained bysubstituting the address MNFI_No for the MNFI_SRP before the MNFI_No isincremented in step S120. The substitution is performed in step S117.The address MNFI_No to be substituted is specified by the MNFI_No beforethe increment. As a result, in step S116, the address MNFI_SRP iscompared with the previous address MNFI_SRP (“ADDR_A”). When theMNFI_SRP [MNFI_No] is no smaller than the ADDR_A, the control goes tostep S119, where all MNFITs are deleted. This completes the checkprocess.

[0130] Up to now, an embodiment of the present invention has beendescribed. However, this embodiment is described only as a systemexample that is expected to provide the best effect at present. Thepresent invention can have many variations as well without deviatingfrom the essence of the present invention. The following are therepresentatives of such variations.

[0131] (A) In the above embodiment, the recording/playback apparatus maybe used as a VCR for home use. Also, the recording/playback apparatusmay be used as a peripheral apparatus of a computer. In the latter case,the recording/playback apparatus is connected with the computer via aninterface conforming to the SCSI, IDE, or IEEE1394 standard.

[0132] (B) In the above embodiment, video streams and audio streams aremultiplexed into VOBs. However, sub-picture data that is generated bycompressing subtitles may also be multiplexed.

[0133] (C) The procedures described in the above embodiments withreference to flowcharts (FIGS. 27-36) may be achieved as amachine-language program. The program may be recorded onto a recordingmedium such as an IC card, an optical disc, or a floppy disk to bedistributed or sold. The machine-language program may be installed foruse onto a general-purpose computer. The computer can achieve thefunctions of the recording/playback apparatus described in the aboveembodiment, by executing the installed machine-language program.

[0134] Although the present invention has been fully described by way ofexamples with reference to the accompanying drawings, it is to be notedthat various changes and modifications will be apparent to those skilledin the art. Therefore, unless such changes and modifications depart fromthe scope of the present invention, they should be construed as beingincluded therein.

What is claimed is:
 1. A recording/playback apparatus for an opticaldisc on which a video object and management information of the videoobject are recorded, the recording/playback apparatus comprising: adetecting unit operable to detect a failure in the managementinformation recorded on the optical disc inserted in therecording/playback apparatus; a state transition control unit operableto change a state of the inserted optical disc to (a) a first state inwhich reading/writing of the inserted optical disc is not available ifthe detected failure is a serious failure and (b) a second state inwhich reading/writing of the inserted optical disc is available butplayback of the video object is not available if the detected failure isa light failure; and a writing unit operable to write data onto theoptical disc if the state of the inserted optical disc is changed to thesecond state.
 2. The recording/playback apparatus of claim 1, whereinthe serious failure is that the management information has beendestroyed by other data overwritten thereon, and the light failure isthat the management information contains an invalid parameter.
 3. Therecording/playback apparatus of claim 2, wherein the invalid parameteris (a) a parameter indicating that the video object has been encoded forcompression by an out-of-spec encoding method, (b) a parameterrepresenting a playback end time of the video object that is earlierthan a playback start time of the video object, or (c) a parameterrepresenting a playback start time of the video object that is laterthan a playback end time of the video object.
 4. The recording/playbackapparatus of claim 1, wherein the management information specifies thewhole or part of the video object as a playback section, and the seriousfailure is that the management information has been destroyed by otherdata overwritten thereon, and the light failure is that at least a startpoint or an end point of the specified playback section is incorrect. 5.The recording/playback apparatus of claim 4, wherein the start point orthe endpoint of the specified playback section is incorrect if (a) thestart or end point is earlier than a start point of the video object,(b) the start or end point is later than an end point of the videoobject, (c) the end point is earlier than the start point of thespecified playback section, and (d) the start point is later than theend point of the specified playback section.
 6. The recording/playbackapparatus of claim 1, wherein the video object includes a plurality ofblocks compressed by a plurality of variable-length encoding methods,the management information indicates correspondence between entrynumbers, sizes, and playback times of the plurality of blocks, and theserious failure is that the management information has been destroyed byother data overwritten thereon.
 7. The recording/playback apparatus ofclaim 6, wherein the state transition control unit changes the state ofthe inserted optical disc to a third state in which reading/writing ofthe inserted optical disc is available but editing of the video objectis not available, if the detected failure is that size or entry numberof a block in the management information is incorrect.
 8. Arecording/playback apparatus for an optical disc on which a video objectand management information of the video object are recorded, therecording/playback apparatus comprising: a detecting unit operable todetect a failure in the management information recorded on the opticaldisc inserted in the recording/playback apparatus; a state transitioncontrol unit operable to change a state of the inserted optical disc to(a) a first state in which reading/writing of the inserted optical discis not available if the detected failure is a serious failure, (b) asecond state in which reading/writing of the inserted optical disc isavailable but playback of the video object is not available if thedetected failure is a first light failure, and (c) a read only state ifthe detected failure is a second light failure; a writing unit operableto write data onto the optical disc if the state of the inserted opticaldisc is changed to the second state; and a playback unit operable toplay back the video object recorded on the inserted optical disc if thestate of the inserted optical disc is changed to the read only state. 9.The recording/playback apparatus of claim 8, wherein the serious failureis that the management information has been destroyed by other dataoverwritten thereon, (b) the first light failure is that the managementinformation contains an invalid parameter, and (c) the second lightfailure is that the total number of pieces of management informationexceeds a predetermined number.
 10. The recording/playback apparatus ofclaim 9, wherein the invalid parameter is (a) a parameter indicatingthat the video object has been encoded for compression by an out-of-specencoding method, (b) a parameter representing a playback end time of thevideo object that is earlier than a playback start time of the videoobject, or (c) a parameter representing a playback start time of thevideo object that is later than a playback end time of the video object.11. The recording/playback apparatus of claim 1, wherein the managementinformation specifies the whole or part of the video object as aplayback section, the serious failure is that the management informationhas been destroyed by other data overwritten thereon, the first lightfailure is that at least a start point or an end point of the specifiedplayback section is incorrect, and the second light failure is (i) thatthe total number of pieces of management information exceeds apredetermined number or (ii) that a playback section specified by apiece of management information overlaps another playback sectionspecified by another piece of management information.
 12. Therecording/playback apparatus of claim 11, wherein the start point or theend point of the specified playback section is judged to be incorrect if(a) the start point or the end point of the specified playback sectionis earlier than a start point of the video object, (b) the start pointor the end point of the specified playback section is later than an endpoint of the video object, (c) the end point of the specified playbacksection is earlier than the start point of the specified playbacksection, and (d) the start point of the specified playback section islater than the end point of the specified playback section.
 13. Therecording/playback apparatus of claim 8, wherein the video objectincludes a plurality of blocks compressed by a plurality ofvariable-length encoding methods, the management information indicatescorrespondence between entry numbers, sizes, and playback times of theplurality of blocks, and the serious failure is that the managementinformation has been destroyed by other data overwritten thereon, andthe second light failure is that the total number of pieces ofmanagement information exceeds a predetermined number.
 14. Therecording/playback apparatus of claim 13, wherein the state transitioncontrol unit changes the state of the inserted optical disc to a thirdstate in which reading/writing of the inserted optical disc is availablebut editing of the video object is not available, if the detectedfailure is that size or entry number of a block in the managementinformation is incorrect.
 15. A playback apparatus for an optical discon which a plurality of video objects and management information of theplurality of video objects are recorded, each video object is a sequenceof picture data, the management information contains a plurality ofpieces of route information, each piece of route information contains atleast one piece of section information that defines playback routes,each of which is composed of at least one playback section, each pieceof section information specifies a playback section that spans from apiece of picture data to another piece of picture data in a videoobject, the playback apparatus comprising: a detecting unit operable todetect a failure in the management information; a first setting unitoperable to, if the detected failure relates to a video object, setevery piece of route information that contains section informationspecifying a playback section constituting the video object, to“playback not available”; and a second setting unit operable to, if thedetected failure relates to a piece of section information, set only apiece of route information that contains the piece of sectioninformation.
 16. The playback apparatus of claim 15, wherein the failurerelating to a video object is (a) a failure that the video object hasbeen encoded for compression by an out-of-spec encoding method, (b) afailure that a playback end time of the video object is earlier than aplayback start time of the video object, or (c) a failure that theplayback start time of the video object is later than the playback endtime of the video object.
 17. The playback apparatus of claim 15,wherein the failure relating to a piece of section information is (a) afailure that a piece of picture data specified in the piece of sectioninformation as an endpoint of a playback section is earlier than a pieceof picture data specified in the piece of section information as a startpoint of the playback section, or (b) a failure that a piece of picturedata specified in the piece of section information as a start point of aplayback section is later than a piece of picture data specified in thepiece of section information as an end point of the playback section.18. The playback apparatus of claim 15, wherein each piece of sectioninformation contains (a) a time code specifying a piece of picture dataas a start point of a playback section and (b) a time code specifying apiece of picture data as an end point of the playback section, and thefailure relating to a piece of section information is (i) a failure thata time code specifying a piece of picture data as a start point of aplayback section is earlier than a playback start time of the videoobject, or (ii) a failure that a time code specifying a piece of picturedata as an end point of a playback section is later than a playback endtime of the video object.
 19. The playback apparatus of claim 15,wherein each video object is divided into groups, each of which iscomposed of pieces of picture data having correspondence with eachother, the management information contains a plurality of pieces of timemap information that correspond to the plurality of video objects on aone-to-one basis, each piece of time map information indicates, for eachgroup belonging to a video object, correspondence between entry numbers,sizes of a plurality of pieces of picture data contained in the group,and playback times of the plurality of pieces of picture data, and therecording/playback apparatus further comprising a third setting unitoperable to, if the detected failure relates to a piece of time mapinformation, set every piece of route information that contains sectioninformation specifying a playback section of a video objectcorresponding to the piece of time map information, to “editing notavailable”.
 20. The playback apparatus of claim 19, wherein the failurerelating to a piece of time map information is a failure that any of anentry number, a data size, and a playback time indicated by the piece oftime map information is incorrect.
 21. A recording medium on which acomputer-readable program is recorded, the program causing a computer tooperate in accordance with a recording/playback procedure for an opticaldisc on which a video object and management information of the videoobject are recorded, the program causing the computer to execute: adetecting step for detecting a failure in the management informationrecorded on the optical disc inserted in the computer; a statetransition control step for changing a state of the inserted opticaldisc to (a) a first state in which reading/writing of the insertedoptical disc is not available if the detected failure is a seriousfailure and (b) a second state in which reading/writing of the insertedoptical disc is available but playback of the video object is notavailable if the detected failure is a light failure; and a writing stepfor writing data onto the optical disc if the state of the insertedoptical disc is changed to the second state.
 22. A program for causing acomputer to operate in accordance with a recording/playback procedurefor an optical disc on which a video object and management informationof the video object are recorded, the program causing the computer toexecute: a detecting step for detecting a failure in the managementinformation recorded on the optical disc inserted in the computer; astate transition control step for changing a state of the insertedoptical disc to (a) a first state in which reading/writing of theinserted optical disc is not available if the detected failure is aserious failure and (b) a second state in which reading/writing of theinserted optical disc is available but playback of the video object isnot available if the detected failure is a light failure; and a writingstep for writing data onto the optical disc if the state of the insertedoptical disc is changed to the second state.
 23. A recording/playbackmethod for an optical disc on which a video object and managementinformation of the video object are recorded, the recording/playbackmethod comprising: a detecting step for detecting a failure in themanagement information recorded on the optical disc inserted in thecomputer; a state transition control step for changing a state of theinserted optical disc to (a) a first state in which reading/writing ofthe inserted optical disc is not available if the detected failure is aserious failure and (b) a second state in which reading/writing of theinserted optical disc is available but playback of the video object isnot available if the detected failure is a light failure; and a writingstep for writing data onto the optical disc if the state of the insertedoptical disc is changed to the second state.
 24. A recording medium onwhich a computer-readable program is recorded, the program causing acomputer to operate in accordance with a recording/playback procedurefor an optical disc on which a video object and management informationof the video object are recorded, the program causing the computer toexecute: a detecting step for detecting a failure in the managementinformation recorded on the optical disc inserted in the computer; astate transition control step for changing a state of the insertedoptical disc to (a) a first state in which reading/writing of theinserted optical disc is not available if the detected failure is aserious failure, (b) a second state in which reading/writing of theinserted optical disc is available but playback of the video object isnot available if the detected failure is a first light failure, and (c)a read only state if the detected failure is a second light failure; awriting step for writing data onto the optical disc if the state of theinserted optical disc is changed to the second state; and a playbackstep for playing back the video object recorded on the inserted opticaldisc if the state of the inserted optical disc is changed to the readonly state.
 25. A computer-readable program for causing a computer tooperate in accordance with a recording/playback procedure for an opticaldisc on which a video object and management information of the videoobject are recorded, the program causing the computer to execute: adetecting step for detecting a failure in the management informationrecorded on the optical disc inserted in the computer; a statetransition control step for changing a state of the inserted opticaldisc to (a) a first state in which reading/writing of the insertedoptical disc is not available if the detected failure is a seriousfailure, (b) a second state in which reading/writing of the insertedoptical disc is available but playback of the video object is notavailable if the detected failure is a first light failure, and (c) aread only state if the detected failure is a second light failure; awriting step for writing data onto the optical disc if the state of theinserted optical disc is changed to the second state; and a playbackstep for playing back the video object recorded on the inserted opticaldisc if the state of the inserted optical disc is changed to the readonly state.
 26. A recording/playback method for an optical disc on whicha video object and management information of the video object arerecorded, the recording/playback method comprising: a detecting step fordetecting a failure in the management information recorded on theoptical disc inserted in the computer; a state transition control stepfor changing a state of the inserted optical disc to (a) a first statein which reading/writing of the inserted optical disc is not availableif the detected failure is a serious failure, (b) a second state inwhich reading/writing of the inserted optical disc is available butplayback of the video object is not available if the detected failure isa first light failure, and (c) a read only state if the detected failureis a second light failure; a writing step for writing data onto theoptical disc if the state of the inserted optical disc is changed to thesecond state; and a playback step for playing back the video objectrecorded on the inserted optical disc if the state of the insertedoptical disc is changed to the read only state.
 27. A recording mediumon which a computer-readable program is recorded, the program causing acomputer to operate in accordance with a playback procedure for anoptical disc on which a plurality of video objects and managementinformation of the plurality of video objects are recorded, each videoobject is a sequence of picture data, the management informationcontains a plurality of pieces of route information, each piece of routeinformation contains at least one piece of section information thatdefines playback routes, each of which is composed of at least oneplayback section, each piece of section information specifies a playbacksection that spans from a piece of picture data to another piece ofpicture data in a video object, the program causing the computer toexecute: a detecting step for detecting a failure in the managementinformation; a first setting step for, if the detected failure relatesto a video object, setting every piece of route information thatcontains section information specifying a playback section constitutingthe video object, to “playback not available”; and a second setting stepfor, if the detected failure relates to a piece of section information,setting only a piece of route information that contains the piece ofsection information.
 28. A computer-readable program for causing acomputer to operate in accordance with a playback procedure for anoptical disc on which a plurality of video objects and managementinformation of the plurality of video objects are recorded, each videoobject is a sequence of picture data, the management informationcontains a plurality of pieces of route information, each piece of routeinformation contains at least one piece of section information thatdefines playback routes, each of which is composed of at least oneplayback section, each piece of section information specifies a playbacksection that spans from a piece of picture data to another piece ofpicture data in a video object, the program causing the computer toexecute: a detecting step for detecting a failure in the managementinformation; a first setting step for, if the detected failure relatesto a video object, setting every piece of route information thatcontains section information specifying a playback section constitutingthe video object, to “playback not available”; and a second setting stepfor, if the detected failure relates to a piece of section information,setting only a piece of route information that contains the piece ofsection information.
 29. A playback method for an optical disc on whicha plurality of video objects and management information of the pluralityof video objects are recorded, each video object is a sequence ofpicture data, the management information contains a plurality of piecesof route information, each piece of route information contains at leastone piece of section information that defines playback routes, each ofwhich is composed of at least one playback section, each piece ofsection information specifies a playback section that spans from a pieceof picture data to another piece of picture data in a video object, theplayback method comprising: a detecting step for detecting a failure inthe management information; a first setting step for, if the detectedfailure relates to a video object, setting every piece of routeinformation that contains section information specifying a playbacksection constituting the video object, to “playback not available”; anda second setting step for, if the detected failure relates to a piece ofsection information, setting only a piece of route information thatcontains the piece of section information.